CS Awesome - Unit 7 Vocabulary

ArrayLists

Autoboxing

Autoboxing

Automatically wrapping a primitive type in a wrapper class object. For instance if you try to add an int value to a list, it will automatically be converted to an Integer object.

Abstract Method

A method that only has a declaration and no method body (no code inside the method).

ArrayList

An ArrayList can hold many objects of the same type. It can grow or shrink as needed. You can add and remove items at any index.

Add

You can add an object to the end of a list using listName.add(obj). You can add an object at an index of a list using add(index,obj). This will first move any objects at that index or higher to the right one position to make room for the new object.

Declaration

To declare an ArrayList use ArrayList<Type\> name, where Type is the class name for the type of objects in the list. If you leave off the <Type\> it will default to Object.

Creation

To create an ArrayList use new ArrayList<Type\>, where Type is the class name for the type of objects you want to store in the list. There are other classes that implement the List interface, but you only need to know the ArrayList class for the exam.

Get

To get an object at an index from a list use listName.get(index).

Index

You can access and set values in a list using an index. The first element in a list called list1 is at index 0 list1.get(0). The last element in a list is at the length minus one - list1[list1.size() - 1].

Remove

To remove the object at an index use ListName.remove(index). This will move all object past that index to the left one index.

Set

To set the value at an index in a list use listName.set(index,obj).

Size

Use listName.size() to get the number of objects in the list.

Wrapper Class

Classes used to create objects that hold primitive type values like Integer for int, Double for double and Boolean for boolean.

Unboxing

Automatically converting a wrapper object like an Integer into a primitive type such as an int.